A nickel catalyst promotes the multicomponent coupling reaction of diketene, an alkyne, and Me2Zn to provide 3-methylene-4-hexenoic acids in excellent yields. Under similar conditions, the combination of the nickel catalyst and Et2Al(OEt) promotes a cycloaddition reaction involving dimerization of an alkyne to furnish phenylacetic acids. In the presence of PPh3, a formal [2+2+1+1] cycloaddition reaction proceeds to afford regioisomeric phenylacetic acids via cleavage of the C=C bond.

Abstract:In the presence of Ni-catalyst and triethylborane, N,O-acetals prepared from glycolaldehyde and glyceraldehyde with primary amines in situ underwent homoallylation with conjugated dienes to provide 2-amino-5-hexenols in high regio-and stereoselectivity. Under similar reaction conditions, N,O-acetals from carbohydrates with primary amines provided the corresponding polyhydroxy-bishomoallylamines in good to reasonable yields.

A nickel catalyst promotes the multicomponent coupling reaction of diketene, an alkyne, and Me2Zn to provide 3‐methylene‐4‐hexenoic acids in excellent yields. Under similar conditions, the combination of the nickel catalyst and Et2Al(OEt) promotes a cycloaddition reaction involving dimerization of an alkyne to furnish phenylacetic acids. In the presence of PPh3, a formal [2+2+1+1] cycloaddition reaction proceeds to afford regioisomeric phenylacetic acids via cleavage of the CC bond.

Efficient and Selective Formation of Unsaturated Carboxylic and Phenylacetic Acids from Diketene. -The Ni(acac) 2-catalyzed reaction of diketene with alkynes is investigated. In the presence of Me 2Zn 3-methylene-4-hexenoic acids (IV) are obtained whereas Et2Al(OEt) as Lewis acid promotes the formation of arylacetic acids. Interestingly, the regioselectivity of arylacetic acid formation can be completely reversed by addition of PPh 3 as co-catalyst. -(MORI, T.; AKIOKA, Y.; KAWAHARA, H.; NINOKATA, R.; ONODERA, G.; KIMURA*, M.; Angew. Chem., Int. Ed. 53 (2014) 39, 10434-10438, http://dx.doi.org/10.1002/anie.201404816 ; Grad. Sch. Eng., Nagasaki Univ., Nagasaki 852, Japan; Eng.) -Mais 11-070